Electrical oscillator



F. K. VREELAND.

ELECTRICAL OSCILLATOR APPucMmu HLED MAY 5, 19x9.

1,340,- 1 93. Patehwa May 18,1920.

0 S! wvevvtoz WW6 7e t e 5 vit Q if M 829,934 I have 1 tained electrical oscilla supplied to uia'rrnn STATES PATENT OFFICE.

rnnnnnrcx K. VR-EELAND, or MONTCLAIR, NEW JERSEY.

ELECTRICAL OMILLATOB.

To all whom it may concern:

Beit known that I LAND a citizen of the United States, residing at Montcl'air, in the county of Essex and State of New Jerse 55 Liberty street, ew York city,) have invented certain new and useful Improvements in Electrical Oscillators, of which the fol lowing is a s ecification.

The invention herein described relates to an improvement in electrical oscillators of the vacuum tube or electron relay type, whereby greatly improved operation is secured, particularly in the matter of purity of the wave form.

In my U. S.

described a method and apundamped' or susions by utilizing an electrostatic or magnetic field excited by the oscillations to control the flow of energy in a vacuum tube or other sensitive gap, in such a manner that increments of energy are paratus for generatin chronism with the oscillations. One form of the invention specifically described utilizes theeflect of an electrostatic field upoh the discharge of cathode particles in a vacuum tube as a means of'electrically communicat in'g energy in the tube in such manner as to add energy to the oscillating circuit in syn c'hronism with the oscillations. (Patent No. 829,447, page 1, lines 56-81.)

In recent years great improvements have been made in thermionic'tubes, whereby the effect ofan electrostatic field, set-up between the cathodekand a third control electrode or "qr-id controls in a highly elficient manner the i .llow of thermionic ener I between the cathode and'the anode. This a paratus is so associated with an oscillating circuit that the i oscillations act through the control electrode to produce the electrostatic comn'iutaiting field, and the variations in anode current thus produced supply energy to the oscillat-' circuit.

"in the vacuum tube oscillator as ordinarily employed to-day, a three electrode thermionic tube, with its appropriatesource of diled to'an oscillatrect current energy, is con" ingcircuit with a fee -back connection, whereby the flow of energy through thetube is controlled by the oscillations and energy is supplied to the oscillating circuit in sync ronism with the oscillations. Ordinarily the oscillating circuit is directly connected to (post-ofiice address No.-

Patents Nos. 829,44 and- Speciflcation of Letters Patent.

Patented May 18, 1920.

i Application filed Hair 15, 1919. Serial No. 297,224.

the thermionic generator tube, the feed-back connection being associated'with this circuit in any one of several well known" ways.

The result of this arrangement is an oscillating current whose wave form is very far from sinusoidal. This is due to the fact that the Wave form of the energy supply is not itself sinusoidal, and the disposition and the proportions of the oscillating circuit are such that it is incapable of smoothing out the oscillating circuit in synigh impedance,

harmonics. As a consequence, when it is desired to secure an approximately pure wave form from such a device it is usual to employ filters or other equivalent devices to sift out the overtones.

The. present invention provides means whereby a current wave of great purity can be secured directly without the use of filters or other extraneous means.

An oscillating circuit, when fed bya source of energy whose waveform is not sinusoidal, will execute approximately pure sinusoidal oscillations only if its inductance and capacity reactances'are large with respect tothe'other impedances of the systen'r with which it is associated.

The thermionic bulbs ordinarily employed possess usually a high, and sometime a very and it isusually impracticable 'to construct an oscillatin circuit of sufficient reactances to be a sti 'oscillator when connected directly to such a tube.

By means of thepresent invention I am able to use an oscillating circuit of moderate capacity and inductance reactances-which is nevertheless'capable of oscillating with very pure waveform. The requisite stiffness of the oscillating system is secured by coupling the oscillating circuit to th tube and'its associated circuits by a step'down coupling whereby the effective impedances of the tube circuit, as affecting the oscillating circuit are greatly reduced, and the distortions of wave form of the energy supply are mini- ,mizeda This may be done in a variety of we s; v y 7 y a the drawing, Figure l-shows the circuit arrangements o one embodiment of the inventlon, in which the oscillating circuit is coupled to a generator circuit by aninductivecou ling. Fig;

in whic an ,electro's atic coupling is employed. I a i In the arrangement of Fig. 1,- T is a three electrode thermionic bulb havin the usual hot filament F with ,heating attery B 2Thows an arrangement anode A, .and grid or control electrode G. The tubeor enerator-circuit includes .the inductance coi so, b, the latter connected to the anode and the former t9 the grid, which by their mutual inductance accomplish the usual feed-back function, the anode andgridbeing connected to points of opposite potential and the filament to an intermediate point. The generator circuit is completed through a stopping condenser'Cw, across which the anode battery 15* is connected.

The oscillating circuit is connected to the generator circuit through inductive con pling oi the coils a and b to a secondary coil .9, having a relatively small number of turns, whose circuit is closed through the main capacity C and inductance L of the oscillating circuit. The coil 8 is preferably closely coupled to the coils a, I). By virtue of the step down action of the transformer a, bs, the oscillating circuit may be made a stiff oscillator with moderate values of inductance and capacity reactances, while the close coupling of the transformer, a, b-s provides an eflicient energy transfer.

By a close coupling I mean acoupling whereby the coil s embraces the major portion of the field of the coils a and I), thus making the generator circuit practically aperiodic and subject to the frequenc control of the oscillating circuit. The e ect on the oscillating circuit however is equivalent to a loose coupling inasmuch as the inductance of the coil 8 is small compared to the inductance L. The oscillating circuit is therefore effective in selecting oscillations of its own frequency to the practical exclusion of other frequencies, notwithstanding the relatively small absolute values of its reactances, while the reactances of the coils a, b, may be made comparable to the tube impedance, thereby providing an efficient energy transfer.

.The invention is not limited to the pure electromagnetic coupling shown in Fig; 1.

Any one of several forms of coupling may be employed. For example, Fig. 2 shows a purely electrostatic coupling. Here the genorator circuit include condensers a, b, of reactances comparab e to the tube impedance, and a third condenser s of relatively small reactance, which serves as a step down electrostatic coupling between the generator circuit and the oscillating circuit, includ ing the coil L. Suitable connections are employed for providing a conducting path from the power battery to the anode through the inductance L and means such as the leak resistance R,-o'r a negative (I battery, for preventing an accumulation of negative charge on the grid G.

Other arrangements embod ing the invention will readily suggest t emselves to those skilled in the art.

Having now described my invention,

what I claim as new therein and desire to secure by Letters Patent is:

' the secondary of this transformer, substantially as set forth.

3. In an electrical oscillator, a generator tube, a power circuit associated therewith, including the primary of a step .down transformer, and an oscillating circuit in the secondary of this transformer, the primary and secondary coils being closely coupled, substantially as set forth.

4. In an electrical oscillator, a generator tube, a power circuit associated therewigh, an oscillating circuit associated with tie power circuit by a step down coupling, the impedance of the power circuit being comparable to the tube impedance and the sec ondary impedance being relatively small, the reactances of the oscillating circuit be ing large relative to the secondary imped-' ance, substantially as set forth.

5. In an electrical oscillator, a generator tube, a power circuit associated therewith, including the primary of a step down transformenan oscillating circuit in the secondary of this transformer, the primary coil having an impedance comparable to the tube impedance, the secondary having relatively low impedance, and the oscillating circuit having capacity and inductance reactances that are large compared to the secondary impedance, substantially as set forth.

6. In an electrical oscillator, a three electrode generator tube, a source of power connected between two of these electrodes, a power circuit including a feed-back connection between these electrodes and the third electrode, and an oscillating circuit associated with the power circui't'by a'step down coupling, substantially as set forth.

' 7. In an electrical oscillator, a three electrode generator tube, a source of power connected between two of these electrodes, and a power circuit including a feed-back connection between these electrodes and the third electrode, the impedance of the power circuit being comparable to the tube impedance, a secondary element of relatively low impedance associated with the ppwer circuit, and an oscillating circuit including the secondary'element whose reactances are large compared with the secondary impedance, substantially as set forth.

8. In an electrical oscillator, a three electrode generator tube, a source of power connected between two of these electrodes, and a power circuit including a feed-back connection between these electrodes and the third electrode and including a primary coil having an impedance comparable to the tube impedance, a secondary coil of relatively small impcdancecoupled thereto, and an oscillating circuit including the secondary coil having reactances that are large compared to the secondary impedance, substantially as set forth. p

9. In an electrical oscillator, a generator tube, a source of power associated therewith, a still oscillating circuit receiving energy from the source of power by a step down coupling and means whereby the oscillations of the oscillating circuit affect the generator tube to control the supply of energy thereto from the source of power, substantially as set forth.

This specification signed and witnessed this 13th day of May, 1919.

FREDERICK K. VREELAND. lVitnesses FRANK L. DYER, C. D. JORDAN. 

